Gammaherpesviruses are lymphotropic viruses known to induce tumors, particularly in the setting of immunocompromise such as AIDS. Gammaherpesviruses are species-specific, thus limiting our ability to study them in vivo. Murine Gammaherpesvirus-68 (MHV68) mimics key aspects of both EBV and KSHV infection, including the establishment of latency in B cells and the formation of B cell lymphomas. This model allows us to dissect key molecular events involved in in vivo infection and disease. Lytic replication, which occurs during an acute infection, masks the events that prepare the viral genome for latency. Epigenetic modifications of the viral genome have been shown to be essential for regulating gene expression and driving the virus into latency. To identify the key epigenetic events that facilitate long-term MHV68 latency, I will use two similar replication-defective mutant viruses, one that establishes normal B-cell latency, and one that is attenuated for B-cell latency. Using ChIP-Seq analysis, I will determine the location of epigenetic modifications present on these two viral genomes at multiple stages of in vivo infection, including the earliest moments following viral entry. These data will be used to specifically identify epigenetic marks that facilitate the establishment of life-long gammaherpesvirus latency in B cells.